1. Field of Invention
The present invention relates to a method and apparatus for reading a code on an optical element; and more particularly, to a method and apparatus for reading a code on a microbead that is typically 1-1000 microns in size using a Fourier plane analysis technique.
2. Description of Related Art
Tiny microbeads that are individually identifiable have many applications in drug discovery, genomics, chemistry, and security. Microbeads are very small objects, typically 1-1000 microns (um) in feature size. They may be cylindrical, cubic, rectangular, or any other shape. Typically microbeads are composed of silica based glass. Coded microbeads are individually identifiable. There are many methods available to encode microbeads. Known methods for encoding microbeads include fluorescence intensity and/or color, chemical techniques, spatial marks on the particles and radio-frequency encoding. However, the known ways involve using expensive, high resolution, optical techniques for imaging and reading the code off the microbead.
For example, FIG. 1 shows such a spatial imaging technique generally indicated as 10′ for reading encoded particles or microbeads that is known in the art, and includes an input light source 12′ for passing input light through a microbead 14 and imaging optics, including an imaging lens 16, to project an image of the microbead 14 on an imaging plane 18 for reading the image using expensive, high resolution, imaging equipment 20. The imaging lens 16 is arranged between the microbead 14 and the image plane 18 at a distance of two focal lengths from each. The imaging optics are also expensive to provide the high resolution image needed to read or interpret the code on the microbead.
In view of this, there is a need in the industry for a less expensive way to encode and decode microbeads.